Effects of Gamma Irradiation on Microbial Load and Chemical Properties for Preserve Dried Shiitake Mushroom Powder

Abstract

Mushrooms are easily susceptible to microorganism spoilage and insect damage. Thus, the process of preservation is necessary for extending mushroom shelf-life. The objective of this study was to investigate the effects of gamma radiation on microbial analysis, antioxidant activities and chemical constituents of dried shiitake mushrooms. The shiitake powder was irradiated with gamma radiation at doses of 2.5, 5.0, 7.5 and 10 kGy. The irradiated samples were extracted with distilled water using ultrasonic bath. The extract was examined for microbial load, antioxidant activities by means of DPPH, FRAP and total phenolic content. Chemical properties were analyzed for total protein content and β-D-glucan content. The result showed that the total bacterial count was eliminated at a dose of 5 kGy and 2.5 kGy for yeast and mold, respectively. Pertaining to antioxidant activities; Increasing gamma irradiation dose, decreasing DPPH, FRAP and total phenolic content of shiitake powder were observed. At the dose of 10 kGy, the lowest DPPH value 2.07 ± 0.02 mgAAE/g, was achieved. The non-irradiated sample showed the highest value (3.16 ± 0.11 mgAAE/g). The FRAP values of irradiated samples ranged from 40.24 ± 0.41 to 3.16 ± 0.11 µmolFeSO 4 /g. At the dose of 2.5, 5.0, 7.5 and 10 kGy significantly reduced total phenolic acid content (9